1. Field of the Invention
This invention relates to air conditioners and in particular to means for controlling the operation of air conditioners, such as central air conditioners, having outdoor condenser and compressor units and indoor evaporator and thermostatic control units.
2. Description of the Prior Art
Central air conditioners conventionally employ outdoor condenser and refrigerant compressor units which are connected to indoor evaporator units and controls by suitable ducts and wiring for providing relatively high capacity indoor air conditioning. Such systems utilize thermostatic controls which conventionally incorporate manually adjustable means for selecting a desired indoor temperature and automatically controlling the operation of the system to obtain such temperature.
At times, such air conditioning systems may become inoperative for any one of a number of different reasons. Illustratively, the system may be shut down because of a high thermostat setting. Alternatively, the apparatus "Heat-Off-Cool" on-off switch may not be in the "Cool" position. Further, power to the system may be disrupted or the voltage of the power supply may drop to a low level insufficient to permit operation of the system. The power interruption may be momentary or continuous.
Additional malfunctioning problems may arise from clogged air filters, furnace blower or evaporator coils. Malfunctioning of the furnace blower, such as from a blown fuse or a broken drive belt, may also cause a failure of the system. Additionally, where adjustable registers are utilized in the air distribution system, restricted, obstructed, or closed registers may similarly cause a failure of the system.
Additional failures may occur because of failure of the power supply to the outdoor condensing unit. Alternatively, such systems are caused to be inoperative when the outdoor temperature is below a preselected temperature, such as 60.degree. F. A restriction or obstruction of the outdoor condensing unit coil may further cause malfunctioning of the system.
Such malfunctionings heretofore have ordinarily required a check of the system by a service technician inasmuch as the prior systems did not provide for indicating to the user specific information as to the cause of the failure, permitting the user, in certain instances, at least, to remedy the malfunction. The requirement of a service technician, in many cases, has been unnecessary, time-consuming, and costly. It is obviously desirable to permit the user of the apparatus to effect simple restarting of the apparatus where the malfunction is of a simple nature so as to avoid the need for the services of a service technician. It is further desirable to provide to the user some indication as to the nature of the malfunction so that suitable servicing of the apparatus, of which the normal user is capable, can be effected without the need for the services of a service technician. Alternatively, where the malfunction is of the type that should be handled by a service technician, it is desirable to provide an indication of this fact to the user so as to avoid undesirable attempts by the user to restart the system without such service technician services. Further, the indication of the malfunction facilitates repair of the air conditioner by the service technician.
Because of the present energy crisis, the problem of low voltage conditions is becoming more prevalent. Such power supply conditions may cause permanent damage to the system. However, it has been found that, quite often, the low voltage condition is temporary and, thus, it is desirable to provide some means for preventing the air conditioner from starting under low voltage conditions and automatically resetting the system upon restoration of the preselected minimum voltage. Additionally, where the stoppage of the system is caused by a power interruption, it is desirable that the system be automatically restarted upon restoration of the power.
In the case of the other above discussed malfunctionings, the user must make some correction to the system prior to the restarting of the system and, thus, a manual reset of the system is desirable. Thus, before restarting the system where the malfunctioning has occurred because of clogged filters, evaporator coils, outdoor condensing unit coils, blown fuses, etc., these conditions must be corrected before an attempt to restart the system should be made.
A number of prior art patents disclose different controls for use with air conditioning apparatus.
William L. McGrath et al, in U.S. Pat. No. 3,054,271, disclose automatic controls for an air conditioning unit which prevents restarting of the compressor motor until a predetermined period of time has elapsed subsequent to stopping of the motor for any reason. The timing operation is terminated by a failure of the power supply.
U.S. Pat. No. 3,294,987, of Frank Skrbina, shows an overload protective device wherein an overcurrent condition closes a reed switch to disconnect the system from the power supply.
In U.S. Pat. No. 3,307,075, Donald M. Park shows an overcurrent and undercurrent control circuit utilizing a reed switch and having means to prevent operation of the reed switch during the starting of the motor being controlled.
U.S. Pat. No. 3,513,353 of John L. Lansch shows a voltage monitoring circuit which compares the power supply voltage against a reference voltage to control a silicon controlled rectifier for opening the circuit automatically in the event of a high voltage condition.
U.S. Pat. No. 3,525,903 of Alton R. Morris et al shows a reed relay with electromagnetic biasing which operates a power relay to disconnect a load. The reed relay is actuated by the secondary winding of a ground fault current interrupter. A biasing circuit is provided for sensitizing or biasing the reed delay.
Arthur R. Day, III in U.S. Pat. No. 3,585,451 shows a solid state motor overload protection system for protecting the compressor motor as a function of a sample of the peak current drawn by each phase of the motor and the temperature of the motor windings so as to control a motor loading reducer. The control operates to disconnect the motor in the event the overload condition persists for 6 seconds after the load reduction is effected and reloads the motor in the event the overload condition is eliminated prior thereto.
Dieter Eichmann et al, in U.S. Pat. No. 3,587,078, shows a limit sensing device responsive to two limit values comprising a flip-flop amplifier receiving a sensed electrical input and a periodic pulse input. The gate output voltage is indicative of whether or not the variable quantity being supervised has reached either of the two limit values.
Ernie Foldvari et al, in U.S. Pat. No. 3,617,815, shows an impedance switching timer having means for delaying the charging of a condenser for controlling the operation of a motor, such as a compressor motor.
Balthasar H. Pinckaers' U.S. Pat. No. 3,619,668 discloses a minimum off-time circuit having an R-C timing portion which is held in a charged condition during normal operation of the compressor and which prevents restarting of the compressor for a preselected period of time subsequent to an interruption of power to the compressor.
Arthur Reginald Day III et al, in U.S. Pat. No. 3,633,073, show an overload and overcurrent regulation and protection system having current sensors driving Schmitt Trigger circuits operating a motor de-energizing device or controlling a mechanical load decreasing device so as to correct for small overloads without de-energizing the compressor motor. A timer is provided to cause shutdown of the compressor in the event the overload condition continues. The output of the comparator circuits comprise variable pulse width signals proportional to the input signal for controlling the input vanes of the compressor.
Donald G. Harter, in U.S. Pat. No. 3,636,369, shows a refrigerant compressor control-relay for controlling two time delays and arranged to keep a compressor de-energized for a predetermined time and to keep a compressor energized for at least a predetermined time at the initiation of each start cycle. The second time delay means shunts a pressure switch which monitors operation of the compressor during the operating cycle.
U.S. Pat. No. 3,700,914, of George John Granieri et al, discloses a control apparatus for air conditioning systems having a minimum off-time time delay circuit and a time delay circuit associated with a pressure switch connected in the refrigerant circuit so as to prevent operation of the compressor unless the pressure in the supply line reaches a preselected pressure within a predetermined time interval.
A refrigerant compressor motor control is shown in U.S. Pat. No. 3,721,880 of Donald E. Neill having a motor current sensor, a temperature sensor for sensing the temperature of the discharge gas from the compressor, and a thermostat for sensing room temperature. The control provides a signal differentially related to the compressor motor running current and a reset current so as to shut the system down when this differential signal reaches a preselected value. The shutdown period is correlated with the time required to reach the shutdown condition so as to provide a variable off period.
U.S. Pat. No. 3,742,302 of Donald E. Neill discloses a motor relay protection device for refrigerant compressor motor control which control operates similar to that of U.S. Pat. No. 3,721,880 discussed above.
U.S. Pat. No. 3,742,303 of Ernest C. Dageford shows a compressor protector system monitoring the internal temperature of a compressor motor by monitoring the motor current and disconnecting the motor when the current exceeds a preselected value over a preselected period of time. The system may directly monitor high temperature conditions within the compressor and automatically rechecks after a predetermined period of time to determine whether the fault causing the stopping of the compressor has been cleared. The control automatically starts the compressor if the fault has been so cleared and prevents short-cycling by preventing attempted restart until after a predetermined period of time. The circuit includes a comparator controlling a semiconductor and electronic switch which, in turn, control the operation of the compressor motor.
U.S. Pat. No. 3,751,940 of Dean K. Norbeck shows a refrigeration system having a control system for controlling a pre-rotation vane motor and utilizes a sawtooth wave generator in combination with a comparator in effecting the desired control. The output of the comparator circuits comprise variable pulse width signals proportional to the input signal for controlling the input vanes of the compressor.
Gary L. Pollitt, in U.S. Pat. No. 3,757,302, discloses a responsive power-fail detection system for monitoring the amplitude of a power source with means for enabling the system to be restarted in a programmed manner and including a voltage comparator circuit.
U.S. Pat. No. 3,777,187, of Mitchell I. Kohn, shows a controller circuit having an operational amplifier for use with a temperature sensing device.
U.S. Pat. No. 3,777,240 of Donald E. Neill discloses a thermostatic chatter protection means for refrigeration compressor motors. The control permits a contact chatter, which lasts for a preselected short period of time only, to occur without disconnecting the motor and includes a restart timer.
Daniel Joseph Connelly et al, in U.S. Pat. No. 3,817,052, show a control circuit for preventing rapid recycling in automatic systems having means providing two different time delay periods, one of which is utilized subsequent to each compressor shutdown and the other of which is utilized in the normal cycling of the compressor.
U.S. Pat. No. 3,836,790, of Dustin J. Becker, shows an A-C voltage detector detecting both high voltage and low voltage conditions and utilizing comparators for driving bistable devices. A timing network is provided for indicating a fault condition existing for more than a predetermined time for preventing false indication of input voltage faults.